Maine Rep. Chellie Pingree is visiting the Portsmouth Naval Shipyard where fire damaged a nuclear submarine last month.The fire on May 23 damaged the command area and torpedo room aboard the USS Miami.The sub's reactor was not affected.The cause of the fire is still being investigated.The Navy is trying to figure out whether to spend millions of dollars to repair the vessel.Attack subs like the Miami are being deactivated faster than they are replaced, and Navy leaders are trying to find new ways to keep up with combat demands.Pingree, who serves on the House Armed Services Committee, is scheduled to brief reporters in Kittery Monday afternoon.